The ability to print images onto paper and other objects is a technology that has become widely available. Most people have printers attached to their home computers, and some even have machines to create die-cast stickers and custom t-shirts. However, all printers are not the same, and the techniques they use to create a finished product are quite diverse. Here is a description of four little-known printing processes.
The word flexography may not ring a bell, but you would recognize its results immediately if you saw them. An improvement on the older letterpress printing, flexography is the technology behind most printed food packages you see every day. The main benefit of this technique is that it can apply print to almost any surface. It employs inks that dry quickly and are easily cleaned off with an anilox roll cleaner.
If you have ever received promotional coasters or mousepads, hung a do-not-disturb sign on your hotel doorknob, or chosen food from a plastic menu, then you have seen the products of offset lithography in action. Lithography is the art of putting an ink-absorbing image on a smooth surface that otherwise repels ink. The images are then offset, or transferred, to rubber rollers.
This method of printing employs electrostatic energy to attract ink powder directly to a surface without touching it. This technique works because zinc oxide, which coats the paper, conducts static electricity when exposed to light. Electrostatic plotters were some of the earliest types of printers to be used with computers, but most people now use electrostatic laser printers. This is the most common technology used in copy machines, and has the benefits of being faster and offering higher resolution than inkjet printers.
To print using the method of rotogravure, a technician must immerse an engraved cylinder into ink, then rotate it on paper. Invented in the 1800s, it is the method responsible for many old photographs, and newspapers once used it extensively. While it does reproduce images with clarity, a person inspecting the photos with a magnifying glass can see that they consist of thousands of small dots. Modern corporations still use this technique to print packaging and magazines.
The history of printing is a long and fascinating one. From the earliest printing presses to the latest three-dimensional printers, there is a wealth of human innovation represented in the diverse technologies within each one.